Finally built this thing for the mane instead of just buying one. There was a dream of making an artistic voronoi pattern, but after burning $3 of filament on testing the sizing, the prototype was close enough to not have any incentive to print another one. Shampoo bottles vary in size.
A quick goog showed there is no shower caddy designed to stand shampoo bottles upside down & what China does produce is expensive. Maybe there's a need to do it right.